Control circuit for an electromagnetically driven programming shutter

Abstract

The electromagnetically driven programming shutter includes magnets and shutter blade driving coils provided on the respective shutter blades of the shutter and electromagnetically cooperating with the magnets and the shutter blades are actuated for opening and/or closing operation when the driving coils are energized. The present invention provides a votage compensating circuit used as the reference voltage generating circuit which is capable of varying the reference output voltage as a function of the variation in the voltage of the electric source, thereby permitting the controlled proper exposure defining output pulse to be modified so as to compensate for the variation in the actuation of the shutter blades caused by the variation in the electromagnetic force generated by the shutter blade driving coils due to the variation in the voltage of the electric source. Alternatively, a temperature detecting circuit may be provided for detecting the temperature of the shutter blade driving coils indicative of the variation in the current flowing through the driving coils and, hence, indicative of the variation in the electromagnetic force given to the shutter blades, and the temperature detecting circuit is connected to the reference voltage generating circuit. The temperature detecting circuit has such a temperature characteristics that the reference output voltage is modified by the temperature detecting circuit in response to the variation in the temperature thereby permitting the variation in the actuation of the shutter blades caused by the variation in the temperature to be compensate for in order to obtain a proper exposure of the shutter.

What is claimed is: 
     
       1. In a control circuit for an electromagnetically driven programming shutter having magnets and shutter blade driving coils provided on the respective shutter blades of said shutter and electromagnetically cooperating with said magnets, said shutter blades being actuated for opening and/or closing operation when said driving coils are energized, said control circuit having an electric source for energizing said driving coils, a scene light information detecting circuit including a photoelectric element adapted to receive the scene light in coupled relationship to the opening and closing operations of said shutter blades so as to generate a scene light information indicating output voltage, a reference voltage generating circuit adapted to be energized by said electric source so as to generate a reference output voltage for obtaining a proper exposure of said shutter by comparing the same with said scene light information indicating output voltage, and a comparator adapted to receive said scene light information indicating output voltage and said reference output voltage and compare the former with the latter so as to generate a controlled proper exposure defining output pulse, said controlled proper exposure defining output pulse being supplied to said shutter blade driving coils so that said shutter is actuated for the proper exposure in cooperation with said magnets, the improvement wherein said reference voltage generating circuit comprises a voltage compensating circuit capable of varying said reference output voltage as a function of the variation in the voltage of said electric source thereby permitting said controlled proper exposure defining output pulse to be modified so as to compensate for the variation in the actuation of said shutter blades caused by the variation in the electromagnetic force generated by said shutter blade driving coils due to the variation in the voltage of said electric source. 
     
     
       2. Control circuit as set forth in claim 1, wherein said voltage compensating circuit comprises a circuit for varying the duration of said controlled proper exposure defining output pulse in response to the variation in the voltage of said electric source. 
     
     
       3. Control circuit as set forth in claim 1, wherein said shutter comprises springs for urging the respective shutter blades of said shutter to the closed position of said shutter, said shutter blades being driven in the shutter opening direction against the action of said springs when said shutter blade driving coils are energized by said controlled proper exposure defining output pulse. 
     
     
       4. In a control circuit for an electromagnetically driven programming shutter having magnets and shutter blade driving coils provided on the respective shutter blades and electromagnetically cooperating with said magnets, said shutter blades being actuated for opening and/or closing operation when said driving coils are energized, said control circuit having an electric source for energizing said driving coils, a scene light information detecting circuit including a photoelectric element adapted to receive the scene light so as to generate a scene light information indicating output voltage, a reference voltage generating circuit adapted to be energized by said electric source so as to generate a reference output voltage for obtaining a proper exposure of said shutter by comparing the same with said scene light information indicating output voltage, and a comparator adapted to receive said scene light information indicating output voltage and said reference output voltage and compare the former with the latter so as to generate a controlled proper exposure defining output pulse, said controlled proper exposure defining output pulse being supplied to said shutter blade driving coils so that said shutter is actuated for the proper exposure in cooperation with said magnets, the improvement wherein said reference voltage generating circuit comprises a voltage compensating circuit capable of varying said reference output voltage as a function of the variation in the voltage of said electric source thereby permitting said controlled proper exposure defining output pulse to be modified so as to compensate for the variation in the actuation of said shutter blades caused by the variation in the electromagnetic force generated by said shutter blade driving coils due to the variation in the voltage of said electric source, and said control circuit further comprises a first digital conversion circuit for converting said scene light information indicating output voltage into a digital scene light information indicating output signal, a second digital conversion circuit for converting said reference output voltage of said voltage compensating circuit into a digital reference output signal, and an operation processing circuit adapted to receive both said digital output signals so as to generate said controlled proper exposure defining output pulse by said operation processing circuit. 
     
     
       5. Control circuit as set forth in claim 4, further comprising an information introducing circuit for introducing an exposure information such as the film sensitivity into said operation processing circuit. 
     
     
       6. Control circuit as set forth in claim 4, wherein said shutter comprises springs for urging the respective shutter blades of said shutter to the closed position of said shutter, said shutter blades being driven in the shutter opening direction against the action of said springs when said shutter blade driving coils are energized by said controlled proper exposure defining output pulse. 
     
     
       7. In a control circuit for an electromagnetically driven programming shutter having magnets and shutter blade driving coils provided on the respective shutter blades and electromagnetically cooperating with said magnets, said shutter blades being actuated for opening and/or closing operation when said driving coils are energized, said control circuit having an electric source for energizing said driving coils, a scene light information detecting circuit including a photoelectric element adapted to receive the scene light so as to generate a scene light information indicating output voltage, a reference voltage generating circuit adapted to be energized by said electric source so as to generate a reference output voltage for obtaining a proper exposure of said shutter by comparing the same with said scene light information indicating output voltage, and a comparator adapted to receive said scene light information indicating output voltage and said reference output voltage and compare the former with the latter so as to generate a controlled proper exposure defining output pulse, said controlled proper exposure defining output pulse being supplied to said shutter blade driving coils so that said shutter is actuated for the proper exposure in cooperation with said magnets, the improvement wherein said reference voltage generating circuit comprises a voltage compensating circuit capable of varying said reference output voltage as a function of the variation in the voltage of said electric source thereby permitting said controlled proper exposure defining output pulse to be modified so as to compensate for the variation in the actuation of said shutter blades caused by the variation in the electromagnetic force generated by said shutter blade driving coils due to the variation in the voltage of said electric source, and said control circuit further comprises a first digital conversion circuit for converting said scene light information indicating output voltage into a digital scene light information indicating output signal, a second digital conversion circuit for converting said reference output voltage of said voltage compensating circuit into a digital reference output signal, an operation processing circuit adapted to receive both said digital output signals so as to generate a shutter blade opening signal and a shutter blade closing signal which is issued after a controlled time period from the issuance of said shutter blade opening signal corresponding to said scene light information indicating signal as well as to the variation in the voltage of said electric source, and a shutter blade actuating circuit adapted to receive said shutter blade opening signal and said shutter blade closing signal, said shutter blade driving coils being energized upon supply of said shutter blade opening signal to said shutter blade actuating circuit in the direction for driving said shutter blades in the shutter opening direction, while said shutter blade driving coils are switched upon supply of said shutter blade closing signal to said shutter blade actuating circuit so as to be energized in the direction for driving said shutter blades in the shutter closing direction. 
     
     
       8. Control circuit as set forth in claim 7, further comprising an information introducing circuit for introducing an exposure information such as the film sensitivity into said operation processing circuit. 
     
     
       9. In a control circuit for an electromagnetically driven programming shutter having magnets and shutter blade driving coils provided on the respective shutter blades of said shutter and electromagnetically cooperating with said magnets, said shutter blades being actuated for opening and/or closing operation when said driving coils are energized, said control circuit having an electric source for energizing said driving coils, a scene light information detecting circuit including a photoelectric element adapted to receive the scene light in coupled relationship to the opening and closing operations of said shutter blades so as to generate a scene light information indicating output voltage, a reference voltage generating circuit adapted to be energized by said electric source so as to generate a reference output voltage for obtaining a proper exposure of said shutter by comprising the same with said scene light information indicating output voltage, and a comparator adapted to receive said scene light information indicating output voltage and said reference output voltage and compare the former with the latter so as to generate a controlled proper exposure defining output pulse, said controlled proper exposure defining output pulse being supplied to said shutter blade driving coils so that said shutter is actuated for the proper exposure in cooperation with said magnets, the improvement wherein said reference voltage generating circuit comprises a voltage compensating circuit capable of varying said reference output voltage as a function of the variation in the voltage of said electric source, a scene light information compensating means for varying the brightness of the scene light received by said photoelectric element, and driving means controlled by said voltage compensating circuit for driving said scene light information compensating means so as to vary the brightness of the scene light received by said photoelectric element correspondingly to the output of said voltage compensating circuit thereby permitting said controlled proper exposure defining output pulse to be modified so as to compensate for the variation in the actuation of said shutter blades caused by the variation in the electromagnetic force generated by said shutter blade driving coils due to the variation in the voltage of said electric source. 
     
     
       10. Control circuit as set forth in claim 9, wherein said scene light information compensating means comprises a variable aperture diaphragm located in front of said photoelectric element. 
     
     
       11. Control circuit as set forth in claim 9, wherein said scene light information compensating means comprises a variable density neutral gray wedge type filter located in front of said photoelectric element. 
     
     
       12. Control circuit as set forth in claim 9, wherein said shutter comprises springs for urging the respective shutter blades of said shutter to the closed position of said shutter, said shutter blades being driven in the shutter opening direction against the action of said springs when said shutter blade driving coils are energized by said controlled proper exposure defining output pulse. 
     
     
       13. Control circuit for an electromagnetically driven programming shutter having magnets and shutter blade driving coils provided on the respective shutter blades of said shutter and electromagnetically cooperating with said magnets, said shutter blades being actuated for opening and/or closing operation when said driving coils are energized, said control circuit having an electric source for energizing said driving coils, a scene light information detecting circuit including a photoelectric element adapted to receive the scene light in coupled relationship to the opening and closing operations of said shutter blades so as to generate a scene light information indicating output voltage, a reference voltage generating circuit adapted to be energized by said electric source so as to generate a reference output voltage for obtaining a proper exposure of said shutter by comparing the same with said scene light information indicating output voltage, and a comparator adapted to receive said scene light information indicating output voltage and said reference output voltage and compare the former with the latter so as to generate a controlled proper exposure defining output pulse, said controlled proper exposure defining output pulse being supplied to said shutter blade driving coils so that said shutter is actuated for the proper exposure in cooperation with said magnets, wherein the improvement comprises a temperature detecting circuit having a predetermined temperature characteristics and arranged at a position where the temperature of said shutter blade driving coils can be detected thereby, said temperature detecting circuit being connected to said reference voltage generating circuit thereby permitting said reference output voltage to be modified by virtue of the temperature characteristics of said temperature detecting circuit so as to compensate for the variation in the actuation of said shutter blades caused by the variation in the electromagnetic force generated by said shutter blade driving coils due to the variation in the temperature.